Telephone system and apparatus therefor



Sept. 29, 1936. P, BAKER TELEPHONE SYSTEM AND APPARATUS THEREFOR Filed Dec. 6, 1952 2 Sheets-Sheet l Sept. 29, 1936. P. BAKER TELEPHONE SYSTEM AND APPARATUS THEREFOR Filed Dec. 6, 1932 2 Sheets-Sheet 2 Patented Sept. 29, 1936 UNITED STATES TELEPHONE SYSTEM AND APPARATUS THEREFOR Paul Baker, Los Angeles, Calif., assignor to Robert A. Casey, Los Angeles, Calif.

Application December 6, 1932, Serial No. 645,891

r 8 Claims. (Cl.1'791) This invention relates to telephone communicating systems, and particularly to systems for intercommunication between various parts of buildings, such as residences. It isespecially adapted for use between the entrance of a building and various parts of the interior of the building for communicating with callers.

A broad object of the invention is to provide a simple, easily operated and reliable system for speaking communication in either direction be.-

tween two points without the use of the usual portable telephone transmitter and receiver.

A more specific object is to provide in such a system a switching device for reversing the direction of communication without producing undesirable clicks or other noise in the loud speakers employed as receivers.

Other objects and advantages of the invention will be apparent from the following detailed description when read in connection with the drawings in which Fig. 1 is a simplified circuit diagram oi. my system; 7

Fig. 2 is a circuit diagram of my system as it may be modified for use in apartment houses;

Fig. 3 is a sectional view showing the construction of the switch 38 in Fig. 1;

Fig. 4 is a sectional view of the switch shown in Fig. 3, taken at right angles to the view shown in Fig. 3;

Fig. 5 is a cross sectional view taken in the plane 55 of Fig. 4; I

Fig. 6 is a cross sectional view taken in the plane 6-6 of Fig. 4;

Figs. 7, 8, 9, 10 and 11, respectively, are views of the switch taken in the plane 'l-I of Fig. 3, showing the switch in various positions of operation.

My system comprises essentially a loud speaker 4 and microphone assembly adapted for installation in a building adjacent the entrance thereto, and usually in the position normally occupied by the push button for the doorbell, together with a similar loud speaker and microphone as- 45 sembly positioned at some point within the building and operatively connected with the first assembly. .The system is adaptedior communication in either direction, but only in one direction at any one time, the direction of communi- 50 cation being controlled by a switch mounted on the loud speaker and microphone assembly 10- cated within the building. The essential features of the invention will be apparent from the following description with reference to the draw- Referring to Fig. 1, the various elements of my system comprise amicrophone and speaker unit 55 within the building and a microphone and speaker unit 54 at the exterior of the building adjacent the entrance thereof, the speaker 5 of each unit being identified by the letter 8" and the microphone by the letter M. The system also includes a pair of switches .36 and 38 positioned adjacent the inside unit 55 for controlling the operation, an amplifier 56 which may 10 be located at any convenient place in the building, and the necessary wire circuits for interconnecting the various elements. An indicating lamp 31 is also provided and is preferably positioned adjacent the speaker-microphone unit 55. 15

The microphone and loud speaker assembly for use within the building isportable so that it can be moved from one location within the building to another, as desired, and is provided with a flexible cord terminating in a plug which 20 may be of any well known type and adapted to be inserted into a cooperating receptacle to complete the circuit connections.

The switch 36 is a power switch for energizing the amplifier 56 by completing connection of the 25 conductors 58 and 59 from the amplifier to a power supply line 51.

The lamp 3-! is lighted whenever the system is energized by closing the switch 36 and serves as a warning to the one using the set to turn it 30 off when he is through using it.

Referring to Figures 3 to 11, inclusive, the detailed construction of switch 38 is fully shown. Thus it comprises a bushing 39 preferably ,mounted in an aperture in the wall 3| of a 5 cabinet housing the unit 55 and secured in position by a nut 40 threaded thereon. Slidabiy mounted within the bushing 39 is a plunger 4i having a finger-piece 42 secured to the outer end thereof and having a notched head 40 43 on the other end which is movable between the extended ends of a pair of spring contacts 44 and 45. The plunger is normally maintained in its uppermost position by a spiral spring 46 positioned between the nut 40 and the fingerpiece 42. In this uppermost position the lowermost, narrowest portion of the head 43 is between thesprings 44 and 45. The latter are therefore permitted to approach each other until they engage fixed springs 41 and 48, respectively. 50 As the plunger 4| is depressed, various faces on the head 43 engage the springs =44 and 45 and force them. apart in a particularly desirable mannerto be described later. When the springs 44 and 45 are separated they first break contact ward movement of the head 43 as the fingerpiece 42 of the opposite end of the plunger 4| is depressed, spring 45 is moved out of engagement with spring 48, as shown in Figure 8.

As downward movement of head 43 continues, movable spring 44 becomes disengaged from 1 fixed spring 41, as shown in Figure 9. In this position, both movable springs are disconnected from their associated fixed contacts. As downward movement of the head 43 continues, the movable spring 44 is moved outwardly into engagement with'fixed spring 49, as shown in Figure 10. Upon final downward movement of the head 43, the movable spring 45 is forced outwardly into engagement with the fixed spring 50, as shown in Figure 11.

The various springs 44, 45, 41, 48, 49 and 50 are supported from a frame member 5|, which is clamped to the bushing 39 as shown in Figures 3 and 4 and 6.

Thus, referring to Figure 6, the springs are clamped to the frame member 5| by screws 52 and are insulated and spaced from each other by bushings 53 and are insulated from the screws 52 by tub'ular insulating bushings 53.

The head 43 hassubstantially fiat faces which bear against the springs 44 and 45 and to insure that these fiat faces will always be presented to the springs, the plunger 4| is squared and the aperture in the bushing 39in which it slides is squared to correspond therewith, as shown clearly in Fig. 5.

As previously indicated, the speaker and micro phone designated by the general reference numeral 54, is mounted on the exterior of a building, preferably adjacent the entrance thereof, about the position where a doorbell button is ordinarily located. The inner set designated by the reference numeral 55 may be located in any desired part of the building. In practice, it is desirable to wire the building with several outlets in diiferent rooms so that the portable inside set 55 may be moved to any one of the rooms wired for it and connected by inserting a plug connected to set 55 in the receptacle provided therefore, which receptacle is connected by the necessary conductors to the rest of the system.

The amplifier unit 56 may be of any desired type, such as one employing vacuum tubes, and preferably contains a complete power rectifying system so that it may be energized directly from electric light mains 51. Amplifiers of this type are well-known, and it is unnecessary to describe their construction in connection with the present invention. Suflice it to say, that the amplifier is energized from a source of power 51 over conductors 58 and 59 whenever the switch 36 is closed, the latter being connected in series in the conductor I." The lamp 31 is bridged across the conductors 58 and 59 in parallel with the amplifier- 58 so that it is lighted whenever power is applied to the amplifier. The amplifier is provided with a pair of input terminals GI and 62 and a pair of output terminals 63 and 64. A variation of impedance of the external circuit between the inlet terminals 6| and 62, such as is caused by speaking into a microphone connected thereacross, causes corresponding, greatly amplified electrical waves to be applied across the output terminals 63 and 64 so that a loud speaker connected across those terminals will be energized to reproduce the sounds picked up by the microphone. One side of each microphone M, associated with both the inside set 55 and the outside set 54, are connected together by a conductor 65 and to input terminal 62 by a conductor 66. The other side of the microphone M in inside set 55 is connected by a conductor 61 to fixed spring 49 of switch 38 which spring is normally disconnected from any other spring.

When the plunger 4| is maintained in its uppermost position by spring 46, the other side of the microphone M, associated with the exterior set 54,

is connected by conductors 68 to fixed spring 41 of switch 38 which in the normal position of the switch is closed on the movable contact 44; contact 44 in turn is connected by a conductor 69 to input terminal 6| of amplifier 56.

It will be apparent therefore that the microphone M, connected with the exterior set 54, is normally connected to the input of the amplifier 56 at all times.

One side of each speaker S, associated with both the inside set 55 and the outside set 54, are

normally connected together by a conductor 10 and to output terminal 63 of the amplifier 56 by a conductor 1|. The other side of the speaker S, associated with the inside set 55, is connected by a conductor 12 to the fixed spring '48 of switch 38,

which is normally in contact with the movable spring 45; the latter in turn is connected by a conductor 13 to theoutput terminal 64 of the amplifier. The other terminal of the speaker S, associated with the outside set 54, is connected by a conductor 15 to fixed spring 50 on switch 38 which is normally disconnected from the movable spring 45. It will, therefore, be apparent that the-speaker S, associated with the inside set 55, is normally connected to the output terminals of amplifier 56 and the speaker associated with the outside set 54 is normally disconnected from the amplifier.

Assume that the circuit is in the condition just described and that the occupant of the house has theinside set 55 conveniently near him, as on a table by his bed if he has retired, and that a caller approaches the house and rings the doorbell. The occupant of the house thereupon energizes the amplifier by closing the switch 36. He is immediately apprized of the fact that the amplifier is operating by the lighting of the indicating'lamp 31. As soon as the amplifier is energized, the microphone associated with the outside set 54 is operatively connected with the speaker associated with the inside set and the occupant may listen to the conversation of the caller or callers and may be able, in some instances, to

- ascertain their identity. If he is able to ascertain the identity of the callers and does not wish to see them, he can switch the amplifier off without apprizing the callers in any way as to whether he isat home or not. On the other hand, if the occupant is unable to ascertain by listening who the caller is, he may speak with the caller by actuating the switch 38 to connect his microphone with the loud speaker of the exterior set 54.

Asthe switch 38 is actuated by depressing the finger piece 42, movable contact 45 is first separated from the fixed contact 48, as shown in Figure 8. This disconnectathe speaker B of the inside set 55 from the amplifier so that any potentials developed by the amplifier as the microphone is later disconnected will produce no discordant or disturbing sounds in the speaker. As the finger piece 38 and plunger 4| are depressed further the movable contact 44 separates from the fixed contact 41, as shown in Figure 9, thereby disconnecting the microphone M associated with the outside set 54 from the microphone. The breaking of this circuit produces no sound in either speaker for the reason that at that time both speakers are disconnected from the amplifier. Further downward movement of the finger piece 38 and the plunger 4| closes the movable contact 48 with the fixed contact 48, as shown in Figure 10. This connects the microphone M, associated with the inside set 55, with the input terminals 6| and 62 of the amplifier 56. It should be noted again particularly that the connection of this microphone produces no disturbing sound or click in either speaker for the reason that both speakers are disconnected from the output terminals of the amplifier at this time. Final downward movement of the plunger 4| closes the movable contact 45 onto the fixed contact 58, as shown in Figure 11. This connects the speaker S associated with the outside set 54, with the output terminals 68 and of the amplifier 56 and completes the talki g circuit.

It is to be u erstood that although considerable time is required to explain the detailed operation of the switch 38, the operations described really take place in very rapid succession, and in fact as rapidly as the plunger 38 can be depressed. As soon as the plunger is depressed the talking circuit from the inside microphone to the outside microphone is completed as described and the occupant may inquire the identity and business of the caller. Immediately thereafterthe occupant releases the pressure on the button 38 and the-spring 46 reverses the plunger 4| to its normal position in which the outside microphone is again operatively associated with the input terminals of the amplifier and the inside speaker is connected to the output terminals of the amplifier and the caller can give the occupant his name and his business. then hold any further conversation desired'with the caller by pressing the button 42 whenever he desires to talk and releasing it when he, desires to listen to the caller. 'When the conversation is completed the amplifier is de-energized by opening the switch 36,the lamp 81 serving as a warning indicator to this effect.

his to be noted that when the button 42 of switch 38 is released-to operatively connect the outside microphone to the inside speaker, the connections are made and broken in switch 38 in exactly the reverse order in which they were made when the button was depressed. Thus it will be observed that the speaker associated with the outside set 54 is first disconnectedfrom the amplifier by movement of the movable contact 45 away from the fixed contact 58, as shown in Figure 10, and therefore both speakers are disconnected from the amplifier until the final connection between movable contact 45 and fixed contact 48 'is made by upward movement of the plunger.

Thus all connections of the microphones are made between the time that one speaker is disconnected and the other is connected so that under noconditions can any crashes or clicks be heard in the speakers.

With slight circuit modifications and structural Obviously the occupant canv 3 changes, the system described is particularly adapted for use in apartment houm and similar buildings where a single telephone in the foyer or lobby is used to communicate with any one of a plurality of apartments or rooms within the building. Such a system may of course be used in private residences as well as apartment houses where the occupants desire to be able to converse with'a caller from various parts of the house.

As previously described, my system utilizes a loud speaking telephone and a separate microphone at each station. I have found, however, that very satisfactory results can often be obtained by using a single loud speaker unit as" both the transmitting and the receiving elements. Thus it is wellknown that the conventional telephone receiver may be used as a transmitter, its chief defect being its lack of sensitivity. Thus the original telephone transmitter invented by Alexander Graham Bell comprised a simple electro-magnetic receiver. In my system the lack of sensitivity of a loud speaker, when used as a transmitter, is not a serious disadvantage for the reason that the amplifier, which is always used, can be readily adjusted to increase the volume to any desired degree.

I have shown in Fig. 2 a schematic circuit diagram of a'system adaptable for use in apartment houses in which the telephone transmitter and receiver at each station comprises a single loud speaker, the microphone being eliminated in each case.

In Fig. 2 the apparatus located in each apartment or room is shown enclosed in a dotted rectangle designated with reference numerals 88, BI and 82, respectively, and the amplifier and lobby telephone have been shown as enclosed within the dotted line 83, since these 'units cooperate with the different sets of apparatus located in the different apartments. It is obvious, however, that the amplifier need not necessarily be located adjacent the foyer telephone which has been provided with auxiliary movable contacts 44a and.

45a. Contact 44a is attached to and moves si=- multaneously with contact 44' which'corresponds to contact 44 in Fig. l, and'contact 45a moves simultaneously with contact 45' which corresponds to contact 45 in Fig. l. The auxiliary movable contacts 44a and 45a are provided to" the purpose of breaking both sides of the circuits between the loud speaker and the amplifier.

The power switch 86, in Fig. 2, differs from the power switch shown in Fig. 1, in that it is provided, in addition to the contacts 86 in the power circuit of the amplifier, with two pairs of contacts 36a and 3812, respectively, and two pairs of contacts 360 and d, respectively, which close the circuit from the output terminals of the am-' plifier 56' and from the input terminals of the amplifier 56' to the direction-control switch 85 only when the power switch is actuated to energize the amplifier. Obviously, if these auxiliary contacts on switch 86 were not provided, the occupants of all apartments in the building would hear a caller in the foyer whenever the amplifier was energized by actuation of any one of the power-control switches 86. However, with the auxiliary contacts as described, the loud speakers in all apartments and the loud speaker in the foyer are normally disconnected from the amplifier and are connected thereto only when the associated power switch is actuated.

The circuit of Fig. 2 operates as follows: Under normal conditions, all of the switches in each apartment are in the position shown in the circuit. The amplifier 56' is, therefore, de-energized and all of the loud speakers are inoperative to act either as receivers or transmitters. Now assume that a caller enters'the foyer and rings the doorbell of apartment No. 1, the apparatus associated with which is enclosed in dotted rectangle 80. The occupant of apartment No. 1, upon hearing the doorbell, will actuate the power switch 86, thereby energizing the amplifier 56 in the manner described in connection with Fig. 1. Actuation of the power switch 86 simultaneously closes contacts 36a and 3617, thereby completing a circuit from the output terminals of the amplifier 56 to the movable contacts and 45a of the direction-control switch 85, and thence, through the back contacts 48 and 48a. of switch 85, to the terminals of the loud speaker At the same time, the input terminals of the amplifier 56' are connected, through contacts 36c and 36d of power switch 86, and through the mov able contacts 44' and 44a and the back contacts 41' and 41a of switch 85, to the loud speaker 84 in the foyer. Therefore, immediately following the actuation of the power switch 86, the foyer loud speaker 84 is connected to the input terminals of the amplifier and the apartment loud speaker 55' is connected to the output terminals of the amplifier. The caller in the foyer can, therefore, talk to the occupant of apartment No. l, but he will not be heard by the occupants of any of the other apartments for the reasonthat the loud speakers in all the other apartments are disconnected by their associated power switches 86 from the amplifier. When the occupant of apartment No. 1 desires to converse with the caller, he reverses the direction of communication by actuating switch 85 precisely as was described in connection with Fig. 1. Thus, it will be observed that when switch 85 is actuated into its opposite position, the input terminals of the amplifier 56 are connected through the movable contacts 44' and 44a to the fixed contacts 49' and 49a, which contacts, like contacts 48' and 48a, are permanently connected to the loud speaker 55. This speaker being connected to the input terminals of the amplifier, it functions as a transmitter when it is spoken into by the occupant of the apartment. The movement of switch into its opposite position also connects the output terminals of the amplifier, through the auxiliary contacts of switch 86 and through the movable contacts 45 and 45a and fixed contacts 50' and 50a of switch 85, to the loud speaker 84 in the foyer. The occupant of the apartment can then converse with the caller in the foyer.

When the occupant of apartment No. 1 is through conversing with the caller, he actuates the power switch 86 into its normal position, thereby deenergizing the amplifier and disconnecting the loud speaker 55' from the output terminals of the amplifier so that should the amplifier be energized by the occupant of another apartment, the occupant of apartment No. 1 will not hear the :onversation.

It is obvious that the occupant of any one of the apartments designated within the dotted rectangles 80, 8| or 82 may energize the amplifier and connect his loud speaker for communication with the foyer in the exact manner outlined in detail in connection with the equipment in apartment No. 1.

It is to be understood that the switch 85 in Fig. 2 is to be operated in the same general fashion as the switch shown in Figs. 3 to 11, so that the loud speaker which is being used as a receiver is always disconnected from the amplifier before the loud speaker which is being used as a microphone is disconnected, thus preventing any clicksor noises in the loud speakers during the switching operation. Since switch 85, in Fig. 2, may be identical in construction with that shown in Figs. 3 to 11 except for the addition of the auxiliary moving contacts 44a and 45a, and their associated fixed contacts 49a, 41a, 48a and 50a, it is unnecessary to show the construction of switch 85 in detail.

Having fully described the preferred embodiment of this invention, it is to be understood that I do not limit myself to the exact construction herein set forth, which may obviously be varied in detail without departing from the spirit of this invention, but only as set forth in the appended claims.

I claim:

1.In a communication system, a first station and a second station, conductors connecting said stations, a microphone and a receiver at each station, a signaling switch at said first station and a signaling device operable thereby at the second station, and switching means at said second station operable into either of two positions for selectively operatively associating the microphone at either station with the receiver at the other station and rendering inoperative the microphone at said other station and the receiver at said either station.

2. In an intercommunication system, a first station positioned adjacent the entrance of a building and a second station positioned within the building, conductors connecting said stations, a microphone and a receiver at each station, a signaling switch at said first station and a signaling device operable thereby within the building, and switching means at said second station operable into either of two positions for selectively, operatively associating the microphone at either station with the receiver at the other station and rendering inoperative the microphone at said other station and the receiver at said either station.

3. In a communication system, a pair of stations, a microphone and a receiver at each station, means for operatively associating the microphone at either station with the receiver at the other station comprising a switch operable between two positions and having a plurality of contacts for closing the respective microphone and receiver circuits, and means for automatically manipulating said contacts in predetermined succession whereby during movement of said switch from one position to the other the receiver at one station is first disconnected, then the microphone at the other station is disconnected, then the microphone at the first station is connected, and last the receiver at the other station is connected.

4. In a communication system, a pair of stations, a microphone and a receiver at each station, means at one station for operatively associating the microphone at either station with the receiver at the other station, comprising a switch operable between two positions and having contacts thereon for operatively associating the microphone at the one station with the receiver at the other station and rendering inoperative the microphone at the other station and the receiver at the one station when the switch is in one position and for operatively associating the microphone at the other-station with the receiver at the one station and rendering inoperative the microphone at the one station and the receiver at the other station when the switch'is in the other position, and means for maintaining said switch in said last position except when it is manually held in the other position. I

5. In a communication system comprising a pair of stations, each provided with a microphone and a receiver, and circuit means for operatively connecting either of said microphones to the receiver at the other station, a switch for reversing the direction of communication in said system, said switch comprising a pair of movable contacts, each movable between two extreme positions, a pair of fixed contacts associated with each of the respective movable contacts, said movable contacts each normally engaging with one of said fixed contacts, one of said movable contacts being connected to one side of both microphone circuits, and the fixed contacts associated with that movable contact being associated with the opposite sides of the circuits of said respective microphones, the other of said movable contacts being connected to one side of both receiver circuits and the fixed contacts associated with that movable contact being associated with the opposite sides of the circuits of said respective receivers, means for sequentially shifting said two movable contacts through their paths of movement from one extreme position to the other whereby the movable contact associated with said receivers is always disconnected from both of its associated fixed contacts during making and breaking of' the other movable contact with its associated fixed contacts.

6. An intercommunication system for apartment-hotels, and the like, comprising a central station and a plurality of substations, an amplifier having input and output terminals, conductors connecting said stations and said amplifier, a communication-direction control switch movable into two positions and a power switch at each substation, each power switch having contacts for applying power to said amplifier when the switch is in on position, and having other contacts for disabling the telephone at that station when the switch is in the off position, each of said direction control switches serving to connect the input terminals of the amplifier to the central station telephone and toconnect the output terminals of the amplifier to the associated substation telephone when said control switch is in one position and to reverse said connections when the control switch is in its other position.

7. An intercommunication system for apartment-hotels and the like, comprising a central station and a plurality of substations, an amplifier having input and output terminals, conductors connecting said stations and said amplifier, a communication-direction control switch ,movable into two positions and a power switch at each substation,' each power switch having contacts for applying power to said amplifier when the switch is in on position and having other contacts for closing a circuit from the output terminals of the amplifier to the associated direction-control switch when the power-switch is in on position and for breaking said circuit when the power-switch is in off position, and having other contacts for disabling the telephone at that station when the switch is in the off position, each of said direction-control switches serving to connect the input terminals of the amplifier to the central station telephone and to connect the output terminals of the amplifier to the associated substation telephone when said control switch is in one position and to reverse said connections when the control switch is in its other position.

8. In a communication system, a first station and a second station, an amplifier having input terminals and output terminals, conductors connecting said stations and said amplifier, a telephone at each station and switching means at said second station operable in either of two positions for selectively connecting the'telephone at either station to the input terminals of said amplifier and the telephone at the other station to the output terminals of said amplifier, said switch having a plurality of contacts connected to said telephones and said input and output terminals, respectively, and means for automatically manipulating said contacts in predetermined succession whereby during movement of said switch from each position to the other, the one telephone connected to said output terminals is first disconnected therefrom, then the other telephone connected to said input terminals is disconnected therefrom, then the one telephone is connected to the input terminals of the amplifier.

PAUL BAKER. 

